In motor vehicles, the vacuum pump produces a negative absolute pressure of, for example, less than 500 millibars and makes it available in the form of potential energy for the pneumatic power brake unit. The mechanical vacuum pump is mechanically coupled, through a coupling element, with the internal combustion engine, and is thereby mechanically driven. Operation of the vacuum pump to supply the power brake unit is relatively rarely required, for example, at the beginning of operation of the motor vehicle and after each braking procedure. To minimize the wear and energy consumption of the drive of the vacuum pump, the vacuum pump is equipped with a coupling arrangement through which the coupling element, which is mechanically driven by the combustion engine, and the pump rotor, which is embodied as a compressor, can be intentionally locked to one another in a non-rotatable manner or unlocked from one another.
DE 198 54 243 C2 describes an arrangement of motor vehicle units in which a pneumatic friction clutch couples the pump rotor with the coupling element when required. Relatively high forces are required to open or close a friction clutch. Since the friction clutch has a pneumatic actuator, another pressure source must be available for this purpose in order to always be able to switch, which makes the construction relatively complex.